Froth flotation is a process for concentrating minerals from ores. In a froth flotation process, the ore is crushed and wet ground to obtain a pulp. Additives such as mineral flotation or collecting agents and frothing agents are added to the pulp to assist in subsequent flotation steps and the valuable minerals are separated from the undesired, or gangue, portions of the ore. After flotation agents are added, the pulp is aerated to produce a froth. The minerals which adhere to the bubbles of froth are skimmed or otherwise removed and the mineral-laden froth is collected and further processed to further concentrate and purify the desired minerals.
Generally the ore is initially floated to produce a rougher concentrate, the rougher concentrate thereafter being refloated, sometimes in the presence of depressants, to further separate the minerals therein. Typical mineral flotation collectors include xanthates, amines, alkyl sulfates, arenes, sulfonates, dithiocarbamates, dithiophosphates, fuel oil and thiols.
It is a continuing goal in the ore-processing industry to increase the productivity of ore flotation processes and, above all, to provide specific procedures which are selective to one mineral over other minerals present in the treated material.
A bis(organothio) alkane can be produced by boron trifluoride etherate-catalyzed addition of dialkyl disulfide to alkenes (See J. Org. Chem. 50:4390, 1985). However, the reference teaches the use of excess alkenes in a solvent mixture of dichloromethane and nitromethane. Though the reference shows reasonably good yield when alkenes other than 1-alkenes are used, the yield is very poor with 1-alkenes. For example, when excess 3-methyl-1-butene is used to prepare a 1,2-bis(methylthio)-3-methylbutane, the yield is only 5%.